Catalytic hydration of olefins



Patented Feb. 7, i950 2,496,621 1 CATALYTIC HYDRATION or ouzrms Roland F. Decry, Los Angeles, Calif.; now by judicial change of name Roland Frank Deering, assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Application April 30, 1945, Serial No. 591,238

4 Claims. 1 This invention relates to a catalyst which finds use principally in the hydration of unsaturated hydrocarbons. 'More particularly the invention pertains to a new and novel manner of preparthe catalyst occurs when in contact with water vapor. This disadvantage is particularly evidenced in the case of hydration catalysts due ing catalysts for these processes which results 5 to the presence in the feed to the hydration-rein a catalyst possessing physical qualifications action of considerable quantities of steam. superior to the catalysts heretofore employed in Generally it is the object of the present insuch processes. vention to provide a new and novel method of Phosphoric acid or metal salts of phosphoric preparing solid catalysts comprising phosphoric acid have found widespread usage in catalysts m acid, metal phosphates or a combination of the for the hydration of olefins. The essential inmetal phosphates and a phosphoric acid with an gredient of the solid catalysts employed in these adsorbent supporting material. reactions is phosphoric acid which in a majority It is another object of the invention to imof cases constitutes 80% or more of the catalyst prove the art of hydration, by preparing catamixture. Of the various forms of phosphoric 5 lysts which exhibit superior mechanical strength acid, orthophosphoric acid (HsPO4) is preferred to those heretofore employed. for catalysts to be employed in the hydration of More specifically it is the object of my invenolefins. The particular form of phosphoric acid tion to provide'a method for preparing phos-' resulting in the finished catalyst is a function phoric acid containing solid catalysts which posof the temperature at which the finished catalyst sess higher mechanical strength and particularly is dried. The progressive dehydration of one or higher resistance to-loss of mechanical strength more molecules of orthophosphoric acid will rein the presence of moisture than the solid phossult in the formation of pyrophosphoric acid and phoric acid catalysts heretofore employed. subsequently the pyrophosphoric acid may be de- Other objects and advantages of my invention hydrated to the tetraphosphoric acid which in will become apparent to those skilled in the art turn may be dehydrated to the metaphosphoric as the description thereof proceeds. acid. For this reason the temperature at which Generally the catalyst preparation method acthe catalyst preparations, according to this incording to my invention comprises precalcining vention, are dried is held within fairly definite an adsorbent siliceous material such as diatolimits in order to insure the presence of the demaceous earth, kieselguhr, artificially prepared sired form of the acid on the catalyst. silica gels and the like to very high temperatures, The conventional method of preparing a phosfor example, in the range of about 800 C. to phoric acid catalyst comprises mixing the liquid about 1400 C. to impart thereto a high degree acid such as orthophosphoric acid with a powof mechanical strength independent of other condered adsorbent material thereby forming a thick stituents in the catalyst. The calcination may paste which is subsequently dried. The catalyst range from 1 to 20 hours or more in length but may be formed by extrusion of the paste before I have found that best results are obtained in drying by crushing and grading the dried mass, the range of about 3 to about 10 hours. This by pilling the powdered dried mass or the like. precalcined support is subsequently impregnated In this type of preparation the physical strength with phosphoric acid. conveniently orthophosof the catalyst is dependent to a large extent upon the phosphoric acid in the mixture. Adsorbent materials normally employed in the preparation of these catalysts comprise predominately siliceous matter such as diatomaceous earth. kieselguhr, artificially prepared silica gel and the like. A catalyst prepared in this manner is dried at a temperature controlled so as to give in the final composition the particular form of phosphoric acid desired.

Such catalysts possess in the absence of water vapor sufiicient physical strength to withstand continued usage. However, due to the hygroscopic nature of phosphoric acid and due further to the dependence of the catalyst structure phoric acid by soaking the support in a solution of the acid having a concentration of 10 to (H3PO4), or the acid may even contain free phosphorus pentoxide (P205). This impregnation is preferably carried out at room temperature although temperatures as high as 100 C. or higher may be employed.

The impregnated catalyst is subsequently dried at a temperature chosen on the basis of the desired form of the acid in the final composition. In the preparation of a hydration catalyst the drying temperature will be maintained below about 240 C. such as from about C. to about 240 C. so as to prevent a conversion of the.

orthophosphoric acid to pyrophosphoric acid.

1 to about 20 hours or longer, but I have found that the optimum time of drying is between about 4 and about 8 hours.

A catalyst prepared in the above described manner, by imparting to the supporting material a physical structure independent of phosphoric acid, not only possesses a high initial me chanical strength but contrary to the presently employed solid phosphoric acid catalysts exhibits no softening or other mechanical breakdown when exposed to as high as 60% water vapor in the hydrocarbon feed.

It is preferable to use phosphoric acid itself for the impregnation of these siliceous supports, but the salts of this acid may also be used provided an excess of the acid is present. If salts are employed in this manner, those of the metals of the first, second and third transitional groups are preferred. These transitional groups include those elements having electronic struc-' tures such that the difierentiating electron is in the second from the outermost shell; that is, the

outermost shell remains substantially unchanged with two electrons, while the second from the outermost shell is being built up from eight to eighteen electrons. The metals of the first transitional group are those having atomic numbers between 21 and 30 and include scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copperand zinc. Those of the second transitional group have atomic numbers between 39 and 48 and include yttrium, zirconium, columbium, molybdenum, masurium, ruthenium, rhodium, palladium, silver and cadmium. Those of the third transitional group have atomic numbers 57 and '72 to 80 and include lanthanum, hafnium, tantalum, tungsten, radium, osmium, iridium, platinum, gold and mercury. In impregnating the supports with phosphoric acid and the above metallic salts, the support may be immersed first in an aqueous solution of orthophosphoric acid; then the material thus impregnated is further impregnated with an aqueous solution of 'a soluble salt such as thechloride or nitrate of the desired metal or metals. The impregnations may also be carried out in the reverse order. The solid material may be dried between the impregnations if desired, and additional impregnations may also be employed to obtain the desired amounts of salts and acid. Such intermediate drying may also be carried out at temperatures from about 105 C. to about 300 C. for periods of from 1 to 20 hours or longer.

The above catalysts are suitable for the hydration of any olefin but are particularly suitable for the hydration of the normally gaseous olefins such as ethylene, propylene and the butenes. These may be employed in mixtures such as are found in gases produced in cracking operations, for example, or other mixtures. Suitable operating conditions for the hydration of the above olefins lie within temperature ranges of about 150 C. to about 350 C., preferably about 175 C. to 300 C.; pressures between about 1 and 200 atmospheres, preferably above 10 atmospheres; and contact times between about 1 second and 10 minutes. Steam must be-employed,

and the proportion of steam to olefin should be between about and about 75%. The general effects of these reaction conditions are as follows: The lower temperatures, the higher pressures, and the higher steam ratios increase the degree of hydration; the higher temperatures reduce the contact time required; and the higher proportions of steam increase the total condensate obtainable from the product gas while decreasing the concentration of alcohol in the condensate. The conditions of temperature.

, pressure and concentration are so adjusted as to insure the maintenance of the vapor phase reaction. It is possible to conduct the operation in the liquid phase also but it is preferable to employ the vapor phase. When propylene is hydrated, the temperature conditions are preferably somewhat lower than for ethylene, a maximum of about 250 C. being preferable. Slightly lower maximum temperatures are preferred for the higher oleiins.

As an example of the hydration of propylene, a diatomaceous earth-phosphoric acid catalyst prepared as in the above example (using about orthophosphoric acid solution for the impregnation) and having an acidity corresponding to about 40% orthophosphoric acid, was employed in an operation similar to the above hydration operation at a temperature of about 180 C. and a pressure of about 250 pounds per square inch gage. The hydrocarbon feedstock consisted of about to propylene and 5 to 10% propane. and the gaseous stream passed over the catalyst consisted of about 82% of this hydrocarbon feed and 18% steam. The isopropyl alcohol recovered by Condensing the condensibles in the product and separating the water by distillation, amounted to 4.0% of the propylene in the feed. which represents about 90% of the equilibrium value. The operation was continued for about hours without appreciable loss in activity of the catalyst.

Variations in the process of recovery of reaction products such as the use of azeotropic distillation, solvent extraction and the like, recycling of the unreacted gas, use of moving bed or fluid catalyst contactin systems, and other variations which would occur to one skilled in the art to be included in the scope of the invention as defined in the following claims.

I claim:

1. A process for hydrating olefins which comprises contacting said olefins in the presence of about 15% to 75% of water vapor with a hydration catalyst comprising a silica support upon which is distended a catalytic agent of the group consisting. of at least one of the oxygen containing acids of phosphorus and mixtures of the oxygen containing acids and metal salts of phosphorus in which mixtures the acids are in excess. said catalyst having been prepared by 'precalcining the silica support to a temperature between about 800 C. and about 1400 C. for a time sumcient to impart physical strength thereto independent of other constitutents of the catalyst. impregnating said support with said catalytic agent, and drying the impregnated support at a temperature not greater than about 240 C.

2. A process for the hydration of olefins which comprises contacting said olefins in the presence 'of about 15% to 75% of water vapor at a temperature between about C. and 300 C. and superatmospheric pressure with aeatalyst. comprising a silica support upon which is distended an acid of phosphorus which catalyst is prepared by precalcining said silica support to a temperature in the range of about 800 C. to about 1400 0., impregnating said calcined silica support with an acid of phosphorus, and drying the impregnated support at a temperature in the range of about 105 C. to about 240 C.

3. A process for the hydration of normally gaseous olefins which comprises contacting said olefins in the presence of about 15% to 75% of water vapor at a temperature between about 150 C. and 300 C. and superatmospheric pressure with a catalyst comprising a major proportion of di-= atomaceous earth upon which is distended orthophosphoric acid, said catalyst having been prepared by calcining said diatomaceous earth to a temperature between about 800 C. and about 1400 C. for a time between about one hour and twenty hours, and impregnating the so calcined diatomaceous earth with an aqueous solution of said orthophosphoric acid, and drying the impregnated support at a temperature between about 105 C. and about 240 C.

4. A process according to claim 3 in which the olefin is propylene.

ROLAND F. DEERY.

REFERENCES CITED The folioing references are of record in the file of this patent:

UNITED STATES PATENTS 

1. A PROCESS FOR HYDRATING OLEFINS WHICH COMPRISES CONTACING SAID OLEFINS IN THE PRESENCE OF ABOUT 15% TO 75% OF WATER VAPOR WITH A HYDRATION CATALYST COMPRISING A SILICA SUPPORT, UPON WHICH IS DISTENDED A CATALYTIC AGENT OF THE GROUP CONSISTING OF AT LEAST ONE OF THE OXYGEN CONTAINING ACIDS OF PHOSPHORUS AND MIXTURES OF THE OXYGEN CONTAINING ACIDS AND METAL SALTS OF PHOSPHORUS IN WHICH MIXTURES THE ACIDS ARE IN EXCESS, SAID CATALYST HAVING BEEN PREPARED BY PRECALCINING THE SILICA SUPPORT TO A TEMPERATURE BETWEEN ABOUT 800*C. AND ABOUT 1400*C. FOR A TIME SUFFICIENT TO IMPART PHYSICAL STRENGTH THERETO INDEPENDENT OF OTHER CONSTITUTENTS OF THE CATALYST, IMPREGNANTING SAID SUPPORT WITH SAID CATALYTIC AGENT, AND DRYING THE IMPREGNANTED SUPPORT AT A TEMPERATURE NOT GREATER THAN ABOUT 240*C. 